Image pickup apparatus and optical apparatus using the same

Abstract

An image pickup apparatus includes an optical system which includes a plurality of lenses, and an image sensor which is disposed at an image position of the optical system, wherein the optical system has a lens surface positioned nearest to object and a lens surface positioned nearest to image, and includes in order from the object side, a first lens having a negative refractive power, a second lens having a positive refractive power, a third lens having a positive refractive power, and a fourth lens, and an object-side surface of the second lens has a shape which is convex toward the object side, and the following conditional expressions (1) and (2) are satisfied: αmax−αmin<4.0×10 −5 /° C.  (1), and 1.8<Σ d /FL<6.5  (2).

What is claimed is: 
     
         1 . An image pickup apparatus, comprising:
 an optical system which includes a plurality of lenses; and   an image sensor which is disposed at an image position of the optical system, wherein   the optical system has a lens surface positioned nearest to object and a lens surface positioned nearest to image, and includes in order from the object side,   a first lens having a negative refractive power,   a second lens having a positive refractive power,   a third lens having a positive refractive power, and   a fourth lens, and   an object-side surface of the second lens has a shape which is convex toward the object side, and   a resin lens is used, and   a surface of the image sensor is flat, and the following conditional expressions (1) and (2) are satisfied:
   αmax−αmin<4.0×10 −5 /° C.  (1), and
 
   1.8 <Σd /FL<6.5  (2),
 
   where,   α max denotes a largest coefficient of linear expansion among coefficients of linear expansion at 20 degrees of the plurality of lenses,   α min denotes a smallest coefficient of linear expansion among coefficients of linear expansion at 20 degrees of the plurality of lenses,   Σd denotes a distance from the lens surface positioned nearest to object up to the lens surface positioned nearest to image, and   FL denotes a focal length of the overall optical system.   
     
     
         2 . The image pickup apparatus according to  claim 1 , wherein the following conditional expression (3) is satisfied:
   −2.8 <f 1/FL<−0.5  (3),
   where,   f1 denotes a focal length of the first lens, and   FL denotes the focal length of the overall optical system.   
     
     
         3 . The image pickup apparatus according to  claim 1 , wherein the following conditional expression (4) is satisfied:
   −0.5< f 1/ R 1 L< 0.1  (4),
   where,   R1L denotes a paraxial radius of curvature of an object-side surface of the first lens, and   f1 denotes a focal length of the first lens.   
     
     
         4 . The image pickup apparatus according to  claim 1 , wherein the following conditional expression (5) is satisfied:
   15.0<ν d 1−ν d 2<40.0  (5),
   where,   νd1 denotes Abbe number for the first lens, and   νd2 denotes Abbe number for the second lens.   
     
     
         5 . The image pickup apparatus according to  claim 1 , wherein
 in an orthogonal coordinate system in which a horizontal axis is let to be νd2 and a vertical axis is let to be θgF2,   when a straight line expressed by θgF2=αp×νd2+β, where, αp=−0.005 is set,   νd2 and θgF2 of the second lens are included in both of an area determined by the straight line in which a value of β is a lower limit value of a range of the following conditional expression (6) and the straight line in which a value of β is an upper limit value of the range of the following conditional expression (6), and an area determined by the following conditional expression (7):
   0.750<β<0.775  (6), and
 
   12<ν d 2<30  (7),
 
   where,   θgF2 denotes a partial dispersion ratio (ng2−nF2)/(nF2−nC2) of the second lens, and   νd2 denotes Abbe number (nd−1)/(nF−nC) for the second lens, and here   nd, nC2, nF2, and ng2 are refractive indices of the second lens for a d-line, a C-line, an F-line, and a g-line respectively.   
     
     
         6 . The image pickup apparatus according to  claim 1 , wherein the following conditional expression (8) is satisfied:
   0.25<( R 1 L+R 1 R )/( R 1 L−R 1 R )<2  (8),
   where,   R1L denotes a paraxial radius of curvature of the object-side surface of the first lens, and   R1R denotes a paraxial radius of curvature of an image-side surface of the first lens.   
     
     
         7 . The image pickup apparatus according to  claim 1 , wherein the following conditional expression (9) is satisfied:
   0.25< f 2/ f 3<15  (9),
   where,   f2 denotes a focal length of the second lens, and   f3 denotes a focal length of the third lens.   
     
     
         8 . The image pickup apparatus according to  claim 1 , wherein the following conditional expression (10) is satisfied:
   −0.2<( R 3 L+R 3 R )/( R 3 L−R 3 R )<4  (10),
   where,   R3L denotes a paraxial radius of curvature of an object-side surface of the third lens, and   R3R denotes a paraxial radius of curvature of an image-side surface of the third lens.   
     
     
         9 . The image pickup apparatus according to  claim 1 , wherein the following conditional expression (11):
   0.5<Φ1 L /IH<3.0  (11),
   where,   IH denotes a maximum image height, and   Φ1L denotes an effective aperture at the object-side surface of the first lens.   
     
     
         10 . The image pickup apparatus according to  claim 1 , wherein the following conditional expression (12) is satisfied:
   2.5<Σ d/D maxair<8.5  (12),
   where,   Σd denotes the distance from the lens surface positioned nearest to object up to the lens surface positioned nearest to image, and   Dmaxair denotes a largest air space among air spaces between the lens surface positioned nearest to object and the lens surface positioned nearest to image.   
     
     
         11 . An image pickup apparatus according to  claim 1 , wherein
 the optical system includes an apertures stop, and   the following conditional expression (13) is satisfied:
   0.8 <D 1 Ls /FL<5  (13),
 
   where,   D1Ls denotes a distance from the object-side surface of the first lens up to the apertures stop, and   FL denotes the focal length of the overall optical system.   
     
     
         12 . The image pickup apparatus according to  claim 1 , wherein the following conditional expression (14) is satisfied:
   0.85< nd 1/ nd 2<1  (14),
   where,   nd1 denotes a refractive index for the d-line of the first lens, and   nd2 denotes a refractive index for the d-line of the second lens.   
     
     
         13 . The image pickup apparatus according to  claim 1 , wherein a half angle of view is not less than 65 degrees. 
     
     
         14 . The image pickup apparatus according to  claim 1 , wherein the following conditional expression (15) is satisfied:
   0.25 <D 2/FL<2  (15),
   where,   D2 denotes a thickness of the second lens, and   FL denotes the focal length of the overall optical system.   
     
     
         15 . The image pickup apparatus according to  claim 1 , comprising:
 an optical member through which light passes, on the object side of the optical system, wherein   both surfaces of the optical member are curved surfaces.   
     
     
         16 . The image pickup apparatus according to  claim 15 , wherein the following conditional expression (16) is satisfied:
   100 <|Fc /FL|  (16),
   where,   Fc denotes a focal length of the optical member, and   FL denotes the focal length of the overall optical system.   
     
     
         17 . An optical apparatus, comprising:
 an image pickup apparatus according to  claim 1 ; and   a signal processing circuit.